In Complete Warrior, it talks of damage being determined by the object's weight, and sharp objects, such as broken pipe bottles, deal damage equal to twice its weight.

It also speaks of being able to gain an AC bonus from using objects such as a table, bla bla bla.

Well, it doesn't really answer the question of Weapon Finesse. Obviously, I was considering the prerequisite for an improvised weapon to have weapon finesse as an option be of equal to or less weight than the heaviest finessable weapon for your size category that you're proficient with- which is probably the light mace, unless if the DM accepts letting you base the weight of off your size category's weight for the spiked chain.

Also, i think there should be some feats for using Improvised Weapons.


WEAPON PROFICIENCY (IMPROVISED WEAPONS): Your constant use of random objects for combat has made you proficient with them.

Prerequisites- INT 13, any other weapon proficiency

Benefit: Choose a category of Improvised Weapons: Furniture, Utensils, or Tools. You are considered proficient when fighting with improvised weapons of your selected category, and therefore don't take the -4 penalty to attack rolls.

I was trying to figure out what seemed strange about this but then I remembered that the feat I was thinking about was introduced in Pathfinder.

I don't know about finesse-able improv weapons, but if you're looking for some inspiration to base your improv proficiency feat on, you could do worse than look up Catch Off-Guard (Combat)
(If that flat-footed bit seems overpowered, which it did to me, reread until you catch the 'unarmed opponents' which I missed the first three times)

Also, I know in 3.5 you don't often hear of 'traits', but the paladin in my Kingmaker game, Kyrie, has the 'Rough and Ready' trait which allows her to be proficient in any improv weapon that could be considered a part of her profession/craft skill. She has ranks in Profession (farmer) and let me tell you how many times she has beaten down an enemy with her shovel (only 1d8 damage based on the improv weapon guidelines, but flavourful as hell and pretty awesome anyway)